This invention relates to an improved high efficiency cooling system for an integrated circuit chip and, more particularly, to an improved indirect cooling system.
In recent years, there has been a rapid development of high power integrated circuit chips to meet increasing demands on performance and size of electronic systems. These chips have decreased in size while at the same time the number of elements on the chips has grown, resulting in an increase in heat generation. There thus exists a need for an improved cooling system for such an integrated circuit chip.
Cooling systems for electronics systems can be conveniently divided into two categories--air cooling and liquid cooling. For the majority of low to medium power electronic systems, air cooling is sufficient. Air cooling is relatively inexpensive and easy to incorporate into most system designs. For extremely low power systems, natural convection cooling may be used. In this approach, air movement is induced by thermal density variations caused by heating of the system, and this is sufficient to carry away excess heat. For systems with higher power levels, forced convection cooling may be used wherein a fan or blower enhances heat transfer coefficients. Enhancements to air cooling, such as increasing surface area by adding fins or analyzing air flow to optimize component placement, can be used for slightly higher power levels.
While air cooling is sufficient for most present day electronic systems, in the future air cooling will be inadequate to handle the expected power levels of the denser integrated circuit chips. Therefore, some form of liquid cooling will be required. Liquid cooling can be divided into two categories--direct and indirect. In direct cooling, the chip comes in direct contact with the coolant, whereas in indirect cooling, heat transfer is accomplished via the package and the chip does not contact the coolant. Of the two, direct cooling is by far the most effective, but selection of the coolant is difficult because it cannot be electrically conductive and coolant fouling due to chemical and mechanical contact reduces heat transfer efficiency. Thus, a need exists for an improved indirect liquid cooling system.